A Zones button calls up a list of the ZonePlayers - each named, during the set-up process, after their location - and what they're playing. Highlight one, press the Music button and you can choose to play Internet radio stations or the contents of your music library. Up to 32 ZonePlayers are supported on a given network, enough I'd say for all but the most palatial of premises.
Incidentally, the network also supports up to 32 controllers, each of which has access to all the ZonePlayers. It's very scalable technology, yes, but an even bigger opportunity for internecine argument.
ZonePlayers can be linked so they pump out the same songs - there's a shortcut to linking them all, handy for parties - and the user interface makes it easy to drop individual ZonePlayers from such groupings, and to add them. Sonos' UI owes plenty to the iPod user interface, but the company has brought plenty of its own ideas to the table, not only with features absent from the portable player, like the ability to queue up songs; add, move and remove them from the list; and save the queue for future use.
Options like these are selected from three buttons place immediately below the screen and which activate the soft menus along the bottom of the display. The panel's not huge, but there's plenty of room for track details, status information and album art - the controller can even work with iTunes ideosyncratic method of encoding album covers in MP3 files. The display is clear and easy to read, and the UI pleasingly laid out upon it.
The only flaw is the nice-but-unnecessary way menus and UI screens fade and slide in and out. It looks good but it feels slow, either because it's taxing the on-board processor, or Sonos has simply timed it that way. Whatever, it means the controller feels slightly unresponsive. It isn't - press the Back button three times quickly in succession to go from the controller's Advanced Settings menu back to the Music menu, and you'll go straight there; the intervening screens are simply skipped. But I'd like the UI to move as fast as I do - or at least allow me to turn off the effects to speed up the action.